[HN Gopher] The Quest for a Fusion Drive ___________________________________________________________________ The Quest for a Fusion Drive Author : tectonic Score : 57 points Date : 2022-11-09 17:05 UTC (5 hours ago) (HTM) web link (orbitalindex.com) (TXT) w3m dump (orbitalindex.com) | Symmetry wrote: | In terms of fusion drivers I've always liked NASA's PuFF[1] or | Pulsed Fission Fusion. The idea is to use a normal z-pinch pulsed | fusion setting, which won't normally be self sustaining. But if | you surround the D-T mix with depleted uranium it'll adsorb a lot | of the fast neutrons from the fusion and trigger a round of | fission generating more energy. The recoil against the magnetic | compressor/nozzle should be enough to generate enough energy for | the next pulse and the reaction byproduct are emitted to become | your propellant. | | [1]https://www.nasa.gov/puff | zabzonk wrote: | we don't have fusion power on earth (except for bombs) so why | could we magically create it (and launch it) in space? | zizee wrote: | There is value in creating designs that are feasible if some | technological breakthroughs is made. If we manage to make | fusion work, then someone can then capitalise on the existing | designs. It's also a great motivator for people to work on | those hard problems that could enable many fantastic | possibilities. It's also just fun to let your imagination not | be constrained by what is possible today, but what might be | possible in the future. | [deleted] | yummypaint wrote: | Fusion on earth (that people talk about) is about generating | electricity. Fusion on spacecraft is about shooting out | exhaust gas as quickly as possible and storing energy at high | density. The rocket equation relates the exhaust rate to the | propelent mass requirements, which determines the feasibility | of the spacecraft. It's a completely different optimization | problem, and one that has historically favored nuclear energy | sources in general. | traverseda wrote: | Well, you don't need to care about safety nearly as much. | zabzonk wrote: | safety is not what is limiting fusion development on earth | - we simply can't do it effectively | sbierwagen wrote: | In 1998, Robert A. Freitas published a detailed design of an | artificial red blood cell with several useful properties, | (stores 236 times as much oxygen as a natural red blood cell, | indefinite shelf life) but with the minor downside that it | would require atomically precise diamond fabrication to | actually construct. https://www.tandfonline.com/doi/pdf/10.31 | 09/1073119980911768... | | Was that paper a waste of time? | bobsmooth wrote: | NASA needs to stop being wimps and bring back Project Orion | | https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls... | api wrote: | Ahh, the old devil's pogo stick... | | The thermonuclear Orion could, on paper, achieve up to 10% the | speed of light on an interstellar trajectory at least for a | small payload. It's possible that it could send a probe to the | Centauri system that would arrive in 40-50 years, short enough | to be feasible on human time scales. | choeger wrote: | I never got the fascination for Orion. Why on earth should a | spaceship carry a gigantic pusher plate? Carry hydrogen instead | and put through a conventional fission engine. That gives you a | much more controllable engine and should save you a lot of dry | mass. | api wrote: | As far as I know the iSP (specific impulse) of Orion is a lot | higher, which may result in better overall performance. | | There are some high temperature nuclear rocket engine designs | though, like nuclear gas core rockets. They're crazy reactor | designs you would never try running down here inside a | biosphere but have energy densities far higher than anything | else save a bomb. | pinewurst wrote: | (a) Much much higher ISP even including pusher plate mass | | (b) We can build bombs and pusher plates now ;) | zabzonk wrote: | no "conventional fission engine" has ever flown - there may | be reasons for this | voldacar wrote: | Yeah the reason is that Richard Nixon cancelled Project | Rover, which had long since demonstrated that a safe and | reliable nuclear engine was totally feasible | cjtrowbridge wrote: | There are a lot of reasons why this is a bad idea, not least of | which is the effects of the resulting electromagnetic pulses on | satellites, the earth, and the equipment on board the vehicle | itself. | | There is also the radioactive fallout that would affect human | populations all over the world. | | Detonating nuclear weapons at high altitudes or in space would | also disturb or damage the van allen belts and expose the | surface of the earth to high levels of radiation from solar | winds and cosmic rays. | | And of course there is the fact that it's a violation of | international law to bring nuclear weapons to space or to test | or detonate them in the atmosphere or in space. | politician wrote: | > Detonating nuclear weapons at high altitudes or in space | would also disturb or damage the van allen belts and expose | the surface of the earth to high levels of radiation from | solar winds and cosmic rays. | | Could you please elaborate on the effects of high nuclear | altitude testing on the belts? Preferably, a link to a paper. | pfdietz wrote: | https://en.wikipedia.org/wiki/List_of_artificial_radiation_ | b... | | It wouldn't expose the Earth to cosmic rays, but it would | damage satellites. | Rooster61 wrote: | I've always wondered if we could mitigate this issue by | burning the spacecraft into a parking orbit around the L2 | Lagrange Point on the far side of the moon using conventional | propellant, and then beginning detonation there. Irradiating | Earth is of course a bad idea, but the Earth Moon L2 point | should be plenty far enough away, provides a stable spot from | which to begin pulsing in whatever direction they like as the | moon orbits, and has the added benefit of the moon itself | acting as a shield for the Earth from the radiation. | | It doesn't really matter if we irradiate the hell out of the | far side of the moon. It's been pelted by solar wind and | cosmic radiation since time immemorial. A bit of radiation | from a few nukes should be negligible by comparison. | toss1 wrote: | Sure, those are problems if the Orion method is used inside | the orbital region. | | However, if used after escaping from Earth's gravity well to | accelerate towards distant destinations, the only remaining | issue is international law. Electromagnetic pulses decay as | the inverse square law, radioactive fallout would be outside | the Earth's gravity well and disperse harmlessly in space, | the Van Allen belts are also not near enough to be affected. | | The only real risk would be from accidents while lifting that | much fissile material to space, which could be mitigated by | proper containment vessels (which do add weight and reduce | effective payload, but the total lift may still be worth the | cost) | kappuchino wrote: | Am I the only one to admit thinking "Odd, It makes no sense | returning to hybrid disk + ssd drives(1)". | | Anyway. Way more cool. | | (1) https://de.wikipedia.org/wiki/Fusion_Drive ___________________________________________________________________ (page generated 2022-11-09 23:01 UTC)